Download STAT 244 MINITAB Commands for Generating Confidence Interval

STAT 244
MINITAB Commands for Generating Confidence Interval for µ
Performing a Hypothesis Test for µ,
Confidence Interval and Hypothesis Test for the
Difference of Two Population Means
and Mean of the Differences (Paired Samples)
For the first part of this exercise, we will consider the data given in problem 6.6 page 430 of the
textbook. Enter the data in the data window.
Generating a 95% Confidence Interval for µ with σ Known
1. Click under Stat, then Basic Statistics, then choose 1-Sample Z. The 1-Sample
Z(Test and Confidence Interval) window will appear.
2. In the Samples in columns: box, enter the desired variable.
3. Enter the appropriate population standard deviation.
4. The default confidence level is a 95%. Moreover, the default option for the box Alternative:
is not equal and should not be changed. If another confidence level is desired (e.g., 99%),
click on Options. Enter the appropriate confidence level in the Confidence Level: box.
Click OK.
Generating a 95% Confidence Interval for µ with σ Unknown
1. Click under Stat, then Basic Statistics, then choose 1-Sample t. The 1-Sample
t(Test and Confidence Interval) window will appear.
2. In the Samples in columns: box, enter the desired variable.
3. The default confidence level is a 95%. If another confidence level is desired (e.g., 99%),
click on Options. Enter the appropriate confidence level in the Confidence Level: box.
Click OK. Note that MINITAB calculates the sample standard deviation.
Performing a Test of Hypothesis for a Population Mean µ with Known σ
1. Click under Stat, then Basic Statistics, then choose 1-Sample Z. The 1-Sample
Z(Test and Confidence Interval) window will appear.
2. In the Variables: box, enter the desired variable.
3. Enter the appropriate population standard deviation.
4. Click on the Perform hypothesis test box. Enter the appropriate mean value under the
null hypothesis in the box Hypothesized mean:.
5. The default alternative hypothesis is a ‘not equal’ alternative. Also, the default significance
level is α = 0.05. If you want a different significance level and/or a different form for the
alternative hypothesis, click on Options.
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(a) To change the significance level, replace 95.0 with the desired confidence level. For
example, if α = 0.1, then you will replace 95.0 with 90.0.
(b) Change the form of the alternative hypothesis by going to the Alternative: box.
6. Click OK to exit the Options window. Click OK.
Performing a Test of Hypothesis for a Population Mean µ with Unknown σ
1. Click under Stat, then Basic Statistics, then choose 1-Sample t. The 1-Sample
t(Test and Confidence Interval) window will appear.
2. In the Variables: box, enter the desired variable. Note that MINITAB computes the
sample standard deviation from the given data.
3. Click on the Perform hypothesis test box. Enter the appropriate mean value under the
null hypothesis.
4. The default alternative hypothesis is a ‘not equal’ alternative. Also, the default significance
level is α = 0.05. If you want a different significance level and/or a different form for the
alternative hypothesis, click on Options.
(a) To change the significance level, replace 95.0 with the desired confidence level. For
example, assume α = 0.1. Hence, replace 95.0 with 90.0.
(b) Change the form of the alternative hypothesis by going to the Alternative: box.
5. Click OK to exit the Options window. Click OK.
For the second part of this exercise, we will consider the data given in problem 7.58 page 544
of the textbook. You can let µ1 represent the mean rent for one-bedroom apartments and µ2
represent the mean rent for two-bedroom apartments.
Performing a Test of Hypothesis for a Difference Between Two Population Means
µ1 − µ2 with Independent Samples
1. Click under Stat, then Basic Statistics, then choose 2-Sample t. The 2-Sample
t(Test and Confidence Interval) window will appear.
2. Choose Samples in One Column if the data is in a single column and a second column
denotes the grouping indicator. Enter the desired variable in the Samples: box and the
appropriate grouping variable in the Subscripts: box.
3. In the event that the variables are in different columns, choose Samples in Different
Columns. Enter the desired first variable and then the desired second variable.
4. If we can assume equal but unknown population variance, choose Assume equal variance.
5. The default alternative hypothesis is a ‘not equal’ alternative and the default value of
the mean difference under the null hypothesis is assumed to be zero. Also, the default
significance level is α = 0.05. If you want a different significance level and/or a different
value for the mean difference under the null hypothesis and/or a different form for the
alternative hypothesis, click on Options.
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(a) To change the significance level, replace 95.0 with the desired confidence level. For
example, if we assume α = 0.01, then replace 95.0 with 99.0.
(b) Change the form of the alternative hypothesis by going to the Alternative: box.
6. If a confidence interval for the population mean difference is desired, the alternative hypothesis should be a ‘not equal’ alternative. The appropriate confidence is listed as % CI
for difference.
7. Click OK to exit the Options window. Click OK.
Performing a Test of Hypothesis for Mean of the Difference µd
1. Click under Stat, then Basic Statistics, then choose Paired t. The Paired t(Test and
Confidence Interval) window will appear.
2. In the event that the variables are in different columns, choose Samples in columns. Enter
the desired first variable and then the desired second variable.
3. In the event the data is summarized, choose Summarized data (differences). Enter the
sample size, sample mean, and sample standard deviation.
4. The default alternative hypothesis is a ‘not equal’ alternative and the default value of
the mean difference under the null hypothesis is assumed to be zero. Also, the default
significance level is α = 0.05. If you want a different significance level and/or a different
value for the mean difference under the null hypothesis and/or a different form for the
alternative hypothesis, click on Options.
(a) To change the significance level, replace 95.0 with the desired confidence level. For
example, if we assume α = 0.01, then replace 95.0 with 99.0.
(b) Change the form of the alternative hypothesis by going to the Alternative: box.
5. If a confidence interval for the population mean difference is desired, the alternative hypothesis should be a ‘not equal’ alternative. The appropriate confidence is listed as % CI
for difference.
6. Click OK to exit the Options window. Click OK.
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